What is a holy door and what should I do?

Pope Francis has declared the Jubilee Year of Mercy and asked each diocese to designate a Holy Door.

To gain a plenary indulgence, one must pass through the door during the Year of Mercy or perform one of the spiritual or corporal works of mercy, in addition to the usual conditions for receiving a plenary indulgence:

It is necessary that the faithful be in the state of grace at least at the time the indulgenced work is completed.

A plenary indulgence can be gained only once a day. In order to obtain it, the faithful must, in addition to being in the state of grace:

have the interior disposition of complete detachment from sin, even venial sin;

have gone to Confession;

receive the Holy Eucharist (it is certainly better to receive it while participating in Holy Mass, but for the indulgence only Holy Communion is required);